Email Blacklist Checker

A blacklist checker tells you whether the IP addresses behind your email and website appear on public spam blocklists, one of the most common reasons business email suddenly bounces or lands in junk. Our tool finds the servers that handle your domain's mail, works out their IPv4 addresses, and checks each one against seven free DNS blocklists at the same time. You see exactly which address is listed, on which list, and what to do next, with a link to check Spamhaus yourself.

How to use the Blacklist checker

1. 1 Enter your domainType the domain you send email from, such as example.co.uk. We use it to find both your mail servers and your website address.
2. 2 Run the blacklist checkSign in with your free account and start the check. Every address is looked up on all seven lists in parallel, so results arrive in seconds.
3. 3 Read the result for each IPEach address is labelled as a mail server (with its hostname) or the website, and marked as listed or not listed. Listed rows name the blocklists involved.
4. 4 Check Spamhaus manuallyUse the Spamhaus link in the results to look up the same addresses on its own free lookup page, as we do not query Spamhaus for you.
5. 5 Fix, delist and recheckDeal with the cause, request removal on each list that has you, then run the check again. Results are cached for about ten minutes per domain.

How DNS blocklists work

Most email blocklists are published as DNS zones, a convention written up in RFC 5782. To ask whether 203.0.113.25 is listed, a mail server reverses the four parts of the address, adds the blocklist zone and looks up an A record: 25.113.0.203.bl.example.org. If the name does not exist, the address is not listed. If it returns an address in the 127.0.0.0/8 range, usually 127.0.0.2 or similar, the address is listed, and the exact value can encode the reason or category. Many lists also publish a TXT record at the same name with a short explanation and a link.

Because the check is just a DNS query, receiving servers can run it on every incoming connection in a few milliseconds. That is why a single listing can affect mail to thousands of organisations at once, and why it can clear just as quickly once the list removes you and the cached answers expire.

Which addresses our blacklist checker tests

Blocklists list IP addresses, not domain names, so the first job is finding the right addresses. Our blacklist checker reads your domain's MX records, looks up the IPv4 address of each mail server, and then adds the IPv4 address your domain itself points to, which is normally your website or hosting server. Private and reserved addresses are skipped, and up to six addresses are checked per run.

It is worth understanding what that does and does not cover. MX servers are the machines that receive your mail. On a typical cPanel host the same server also sends it, so checking the MX and website addresses covers the likely problem. If you send through Google Workspace, Microsoft 365 or a newsletter platform, your outgoing mail leaves from that provider's servers instead, and those are managed by the provider. In that case a listing on your web server usually points to a problem with the site, such as an abused contact form, rather than your day-to-day email.

• Only IPv4 addresses are checked, as the free blocklists we use are IPv4 lists.
• If the domain has no MX records and no IPv4 address, there is nothing to look up and the check stops with an explanation.
• Each address is shown with its role, for example "mail server mail.example.co.uk" or "website".

The seven blocklists we check, and Spamhaus

We query seven free lists that allow ad-hoc lookups: SpamCop, PSBL, UCEPROTECT Level 1, Mailspike, NiX Spam, DroneBL and SpamRATS. The lookups go over DNS-over-HTTPS through a public resolver and run in parallel, so 42 queries take seconds rather than a minute.

Some lists refuse to answer queries from large public resolvers and instead return a special code in the 127.255.255.x range. That code means the query was blocked, not that you are listed, so our checker only treats answers in 127.0.0.x as a listing. This avoids the false alarms that simpler tools sometimes show.

Spamhaus is the most influential blocklist, used by a large share of UK and international mail systems, but its terms require a paid data feed for commercial services that query it on behalf of others. Rather than break those terms, we link to the free Spamhaus lookup page, where you can check your own IPs and domain directly.

Reading your blacklist check results

Each address gets one line. A pass means it was not listed on any of the seven lists. A fail names every list that returned a listing code, with advice on finding and fixing the cause. If a provider's support team asks for the exact return code, run the dig command in the examples below for that list.

Not every listing carries the same weight. SpamCop and PSBL listings are triggered by recent spam reports or spam traps and tend to expire on their own once the spam stops. UCEPROTECT Level 1 lists single addresses that hit its traps. DroneBL focuses on compromised machines and open proxies rather than ordinary spam. If you are listed on one smaller list and mail is flowing normally, monitor it and fix the cause. If you are on several, or mail is bouncing with a message that names a list, treat it as urgent.

Why business IPs end up blacklisted

For small UK businesses the cause is rarely deliberate spam. It is usually something sending mail that nobody is watching. Before you request removal, find and stop the source, or you will simply be listed again, and some lists lengthen the listing period for repeat offenders.

• A mailbox password has been guessed or phished, and the account is sending spam through your server.
• A website contact form, newsletter sign-up or WooCommerce account form is being abused by bots to send messages to third parties.
• An outdated WordPress plugin or script has been exploited to send mail directly from the hosting account.
• A neighbour on the same shared IP is sending spam, which affects everyone on that address.
• An office device, printer or old server is misconfigured as an open relay or infected with malware.

Getting delisted and staying off the lists

Once the cause is fixed, visit each list's own lookup page, enter the listed IP and follow its removal process. SpamCop and several others delist automatically after a set period without new reports, often 24 hours. Others offer a removal form, and some offer paid express removal, which you never need to buy. Reputable lists do not require payment to delist, and expiry is free.

If the IP belongs to your hosting company or email provider, raise a support ticket instead of applying yourself. They may need to clean up another customer or move you to a different IP. Afterwards, keep your outgoing mail authenticated with SPF, DKIM and DMARC, send newsletters through a proper email service rather than your web server, add CAPTCHA or rate limits to forms, and rerun the blacklist check after any security incident.

Blacklists are only part of email reputation

A clean blacklist check is good news, but it does not guarantee your mail reaches the inbox. Large mailbox providers such as Gmail and Outlook.com rely mainly on their own internal reputation systems, built from how recipients treat your messages: whether they open them, delete them unread, or mark them as spam. Those scores are not published as DNS blocklists, so no checker can query them directly.

If your IPs are clean but mail still goes to junk, look at authentication first, since SPF, DKIM and DMARC failures are a far more common cause for small UK businesses than listings. Then look at the content and the list you are sending to. Google Postmaster Tools shows the spam complaint rate and domain reputation Gmail sees for your domain once you send enough volume, and Microsoft offers similar data through its Smart Network Data Services programme for IP owners.

Examples you can copy

dig +short 25.113.0.203.bl.spamcop.net A

dig +short 25.113.0.203.bl.spamcop.net TXT

nslookup 25.113.0.203.psbl.surriel.com

1. Note the listed IP and the list name from the results
2. Find the cause: mail logs, compromised accounts, form abuse, outdated plugins
3. Fix it: reset passwords, enable MFA, patch, add CAPTCHA to forms
4. Shared IP? Open a ticket with your host or email provider instead
5. Use the list's own lookup page and removal form, or wait for auto-expiry
6. Rerun the blacklist check after the cached result clears

Common mistakes to avoid

Frequently asked questions